mod_http_oauth2: Tweak formatting of log message No need to `or ""` anymore since Prosody rev e88db5668cfb (0.11.0) and the %q format should produce either (nil) or "http://example"

This module produces more detailed HTTP logs for Prosodys built-in HTTP
server. The format is similar to that of Apache and go into Prosodys
normal logs at the `info` level.